The properties, origins, and evolution of isolated subsets of MSV specific genes were examined. RNA transcription from MSV proviral DNA was studied in viral and chemically transformed cells, and revertants. MSV specified polyproteins were identified in mammalian transformed cells. Properties of various oncornaviral surface proteins such as gp71 and p15E were examined. Limited but specific immunity was achieved in three strains of mice against Friend MuLV after homologous, active gp71 immunization. Seroimmunotherapy was shown to be a better means of disease control. BIBLIOGRAPHIC REFERENCES: Frankel, A. E., and Fischinger, P. J.: Rate of divergence of cellular sequences homologous to segments of Moloney sarcoma virus. J. Virol. 21: 153-160, 1977. Schafer, W., Fischinger, P. J., Collins, J. J. and Bolognesi, D. P.: Role of carbohydrate in biological functions of Friend murine leukemia virus gp71. J. Virol. 21: 35-40, 1977.